From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f197.google.com (mail-pf0-f197.google.com [209.85.192.197]) by kanga.kvack.org (Postfix) with ESMTP id 3E6B36B0279 for ; Thu, 1 Jun 2017 23:09:59 -0400 (EDT) Received: by mail-pf0-f197.google.com with SMTP id a66so69869394pfl.6 for ; Thu, 01 Jun 2017 20:09:59 -0700 (PDT) Received: from ozlabs.org (ozlabs.org. [103.22.144.67]) by mx.google.com with ESMTPS id 6si21511341pfe.109.2017.06.01.20.09.58 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 01 Jun 2017 20:09:58 -0700 (PDT) From: Michael Ellerman Subject: Re: 4.12-rc ppc64 4k-page needs costly allocations In-Reply-To: References: <87h9014j7t.fsf@concordia.ellerman.id.au> Date: Fri, 02 Jun 2017 13:09:54 +1000 Message-ID: <878tlb2igt.fsf@concordia.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain Sender: owner-linux-mm@kvack.org List-ID: To: Hugh Dickins , Christoph Lameter Cc: "Aneesh Kumar K.V" , linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org Hugh Dickins writes: > On Thu, 1 Jun 2017, Christoph Lameter wrote: >> >> Ok so debugging was off but the slab cache has a ctor callback which >> mandates that the free pointer cannot use the free object space when >> the object is not in use. Thus the size of the object must be increased to >> accomodate the freepointer. > > Thanks a lot for working that out. Makes sense, fully understood now, > nothing to worry about (though makes one wonder whether it's efficient > to use ctors on high-alignment caches; or whether an internal "zero-me" > ctor would be useful). Or should we just be using kmem_cache_zalloc() when we allocate from those slabs? Given all the ctor's do is memset to 0. cheers -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org